Silicon Compound Containi-Electron Conjugated-System Molecule and Process for Producing the Same

ABSTRACT

A π-electron conjugate molecule-containing silicon compound represented by the formula (I):  
                 
wherein R1 represents an organic group obtained by combining two or more units constituting plural π-electron conjugate systems, R2 represents a hydrophobic group and X1 to X3, which may be the same or different, respectively represent a group providing a hydroxyl group when it is hydrolyzed or a hydrogen atom.

TECHNICAL FIELD

The invention relates to a n-electron conjugate molecule-containingsilicon compound and a method of producing the same, and, particularly,to a π-electron conjugate molecule-containing silicon compound which isa conductive or semiconductive novel material useful as electronicmaterials and a method of producing the same.

BACKGROUND ART

Besides semiconductors using inorganic materials, semiconductors(organic semiconductors) using organic compounds have been recentlyresearched and developed and the results have been reported becausethese organic semiconductors are simply produced and easily processed,can correspond to the miniaturization of devices and is expected toattain cost reduction in mass-production, and as the organic compounds,various organic compounds having a more variety of functions thaninorganic materials can be synthesized.

It is known that TFTs having large mobility can be produced by utilizingorganic compounds containing a π-electron conjugate molecule among theseorganic materials. As this organic compound, pentacene is reported as atypical example (for example, IEEE Electron Device Lett., 18, 606-608(1997): Non-patent Document 1). In this report, there is the descriptionthat when pentacene is used to produce a semiconductor layer, which isused to form a TFT, the field effect mobility is 1.5 cm²/Vs and it istherefore possible to produce a TFT having a larger mobility thanamorphous silicon.

However, when an organic semiconductor layer having a higher fieldeffect mobility than amorphous silicon as shown above is produced, avacuum process such as a resistance heating vapor deposition method anda molecular beam vapor deposition method is required. This leads to theresult that the production process is complicated and a crystalline filmis obtained only under a specific condition. Also, this method has theproblem that because the adsorption of the organic compound film to thesubstrate in the vacuum process is physical adsorption and therefore,the adsorption strength of the film to the substrate is so low that thefilm is easily peeled off. Generally, the orientation of a substrate onwhich the film is to be formed is controlled by rubbing treatment or thelike to control the orientation of the molecules of the organic compoundin the film to some extent. However, there has been no report concerningthe fact that the conformity and orientation of a compound molecule atthe boundary between the physically adsorbed organic compound film andthe substrate can be controlled by the film formation by physicaladsorption yet.

On the other hand, studies as to the regularity and crystallinity of afilm which have a large influence on the field effect mobility that is atypical guide to the characteristics of a TFT have been recently made byutilizing a self-organizing film using an organic compound that issimply produced.

The self-organizing film means a film which is obtained by combining apart of an organic compound with a functional group present on thesurface of a substrate, is very reduced in defects and has highorderliness, that is, high crystallinity. This self-organizing film isformed on the substrate with ease because it is produced by a verysimple production method. Generally, a thiol film formed on a goldsubstrate and a silicon type compound film formed on a substrate (forexample, a silicon substrate) are known as the self-organizing film, andthe later substrate can be processed by hydrophilic treatment such thata hydroxyl group is allowed to project from its surface. Among thesefilms, a silicon type compound film attracts remarkable attention fromthe viewpoint of high durability. The silicon type compound film isconventionally used as a water-repellent coating and is formed using asilane coupling agent containing, as organic functional groups, an alkylgroup or fluorinated alkyl group having a high water-repellent effect.

However, the conductivity of the self-organizing film is determined byan organic functional group in a silicon type compound contained in thefilm. However, no commercially available silane coupling agent is foundwhich contains a π-electron conjugate molecule as an organic functionalgroup. It is therefore difficult to impart conductivity to theself-organizing film. There is therefore a strong demand for a siliconcompound which is suitable to a device such as a TFT and contains aπ-electron conjugate molecule as an organic functional group.

As such a silicon type compound, a compound is proposed which has onethiophene ring as a functional group on the terminal of a molecule, thethiophene ring being connected with a silicon atom through astraight-chain hydrocarbon group (for example, Japanese Patent No.2889768: Patent Document 1).

Also, there is, for example, a proposal of a method of forming anantistatic film by a chemical deposition method as the self-organizingmethod using an organic molecule (for example, the publication ofJapanese Unexamined Patent Publication No. HEI15 (1993)-202210: PatentDocument 2). In this method, a conductive chemical adsorption filmhaving a conductivity of 10⁻⁵ S/cm or more is formed on the surface of asubstrate having a conductivity of 10⁻¹⁰ S/cm or less through a siloxanetype monomolecular film.

[Non-patent Document 1] IEEE Electron Device Lett., 18, 606-608 (1997)

[Patent Document 1] Japanese Patent No. 2889768

[Patent Document 2] Japanese Unexamined Patent Publication No. HEI5(1993)-202210

DISCLOSURE OF INVENTION Problems that the Invention is to Solve

The compound proposed above ensures the production of a self-organizingfilm that can be chemically adsorbed to a substrate. However, it hasunnecessarily ensured the production of a thin film having highorderliness, crystallinity and electroconductive characteristics enoughto produce electronic devices such as TFTs.

In order to obtain high orderliness, that is, high crystallinity, it isnecessary that high attracting interaction is exerted between molecules.The intermolecular force is constituted of an attractive factor and arepulsive factor, wherein the former is in inverse proportion to the 6thpower of the distance between molecules and the latter is in inverseproportion to the 12th power of the distance between molecules.Therefore, the intermolecular force which is the sum of the attractivefactor and the repulsive factor has the relationship as shown in FIG. 1.Here, the minimum point (the point indicated by the arrow in the figure)indicates the distance between molecules at which the highest attractiveforce is exerted between molecules in the balance between the attractivefactor and the repulsive factor. Specifically, it is important that theintermolecular distance is made to be the closest to the minimum pointto obtain high crystallinity. Therefore, originally, in a vacuum processsuch as a resistance heating vapor deposition method and a molecularbeam vapor deposition method, a film having high orderliness,specifically, high crystallinity is obtained by well controlling theintermolecular interaction between π-electron conjugate molecules onlyin a certain specific condition. It is possible to develop highelectroconductive characteristics only when the film has such the highcrystallinity structured by intermolecular interaction.

On the other hand, the above compound has the possibility of forming atwo-dimensional network of Si—O—Si so that it is chemically adsorbed tothe substrate and also, the orderliness by the intermolecularinteraction between specific long-chain alkyls is obtained. However,this compound has the problem that it has low intermolecular interactionbecause only one thiophene molecule that is a functional groupcontributes to π-electron conjugate system and a spread of theπ-electron conjugate system which is essential for electroconductivityis very small. Even if the number of thiophene molecules which are theabove functional groups could be increased, it is difficult that thefactors forming the orderliness of the film are coordinately andconsistent with the intermolecular interaction between the long-chainalkyl part and the thiophene part.

As to the electroconductive characteristics, only one thiophene moleculewhich is a function group has a large HOMO-LUMO energy gap, giving riseto the problem that only insufficient carrier mobility is obtained evenif a TFT is used in an organic semiconductor layer.

The present invention has been made in view of the above problem and hasthe following object. Specifically, it is an object of the presentinvention to provide a novel π-electron conjugate molecule-containingorganic silicon compound which can be easily crystallized by a simpleproduction method using a solution process to form a thin film, makesthe obtained thin film adsorb to the surface of a substrate firmly toprevent the thin film from being peeled off physically and has highorderliness, crystallinity and electroconductivity, and to provide amethod of producing the organic silicon compound. Another object of thepresent invention is to provide a compound which can secure sufficientcarrier mobility when used as an electronic device such as a TFT and amethod of producing the compound.

Means of Solving the Problems

The inventors of the present invention have made earnest studies toattain the above object and, as a result, found that in order to producea thin film applicable to electronic devices such as TFTs, it isnecessary to use a compound which can form a two-dimensional network ofSi—O—Si and bind with a substrate firmly and can form a thin film whoseorderliness (crystallinity) can be controlled by interaction, namely,intermolecular force of the molecules (here, a π-electron conjugatemolecule) formed on the two-dimensional network of Si—O—Si, and invent anovel π-electron conjugate molecule-containing organic silicon compound.The inventors of the present invention have also found that if ahydrophobic group is introduced into the molecular structure of thecompound, the compound is improved in solubility in an organic solventand a self-organizing film can be uniformly formed when the compound isused.

According to the present invention, there is provided a π-electronconjugate molecule-containing silicon compound represented by theformula (I):

wherein R1 represents an organic group obtained by combining two or moreunits constituting plural π-electron conjugate systems, R2 represents ahydrophobic group and X1 to X3, which may be the same or different,respectively represent a group providing a hydroxyl group when it ishydrolyzed or a hydrogen atom.

According to the present invention, there is provided a π-electronconjugate molecule-containing silicon compound represented by theformula (II):

wherein R1, R2 and X1 to X3 are as defined above, R3 represents ahydrophobic group.

According to the present invention, there is provided a method ofproducing a π-electron conjugate molecule-containing silicon compoundcomprising reacting a compound represented by the formula (III) or (IV):R2-R1-R3-Z  (III)R2-R1-R3-Z  (IV)wherein R1 to R3 are as defined above and Z represents MgX, wherein Xrepresents a halogen atom or Li, with a compound represented by theformula (V):

wherein X1 to X3 are as defined above and Y represents a hydrogen atom,a halogen atom or a lower alkoxy group

to produce the π-electron conjugate molecule-containing silicon compoundrepresented by the formula (I) or (II):

wherein R1 to R3 and X1 to X3 are as defined above.

EFFECT OF THE INVENTION

The organic silicon compound of the present invention has a hydrophobicgroup and therefore has high solubility in a nonaqueous type solvent. Inthe case of, for example, forming a thin film, a solution process whichis a relatively simple method can be applied to this organic siliconcompound.

Also, the organic silicon compound of the present invention forms atwo-dimensional network of Si—O—Si formed between organic siliconcompounds having a π-electron conjugate molecule whereby it ischemically adsorbed to a substrate and the intermolecular interactionamong π-electron conjugate molecules which is the short range forcenecessary for the crystallization of a film is exerted efficiently.Therefore, a thin film which has very high stability and is highlycrystallized can be constituted. Therefore, the resulting film can beadsorbed to the surface of the substrate more firmly than a film formedon a substrate by physical adsorption and can be therefore preventedfrom being peeled off physically. Also, the compound as mentioned abovecan be produced simply.

Also, the network derived from the organic silicon compound constitutingthe thin film is directly connected with an organic residue constitutingthe upper part and a thin film having high orderliness (crystallinity)can be formed by the network derived from the organic silicon compoundand the intermolecular interaction of the π-electron conjugatemolecules. This ensures that carriers are transferred smoothly byhopping conduction in a direction perpendicular to the plane of amolecule. Also, because high electroconductivity is obtained in thedirection of the axis of a molecule, the organic silicon compound may bewidely applied not only to organic thin film transistor materials butalso to devices such as solar cells, fuel cells and sensors as aconductive material.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view for explaining the relationship between intermoleculardistance and intermolecular force.

BEST MODE FOR CARRYING OUT THE INVENTION

The π-electron conjugate molecule-containing silicon compound of thepresent invention is represented by the formula (I) or (II):

wherein R1 represents an organic group obtained by combining two or moreunits constituting plural π-electron conjugate systems, R2 represents ahydrophobic group, R3 represents a hydrophobic group and X1 to X3, whichmay be the same or different, respectively represent a group providing ahydroxyl group when it is hydrolyzed or a hydrogen atom.

Generally, many molecules in which a π-electron conjugate system isspread are sparingly soluble even in organic solvents. On the contrary,the compound of the present invention is improved in solubility in anorganic solvent by the existence of the hydrophobic groups R2 and R3 asshown in the above formulae (I) and (II) and may be therefore applied toa solution process.

Explanations will be furnished as to each structure of the formulae (I)and (II).

First, R1 represents an organic group obtained by combining two or moreunits constituting plural π-electron conjugate systems. Generally, aconjugate double bond has one bond of a π-electron and one bond of aπ-electron and therefore, the term “unit constituting a π-electronconjugate system” means a compound having at least one conjugate doublebond. Specifically, this unit may be selected from the group consistingof groups derived from aromatic hydrocarbons, condensed polycyclichydrocarbons, monocyclic heterocyclic compounds, condensed heterocycliccompounds, alkenes, alkadienes and alkatrienes.

Examples of the aromatic hydrocarbons include benzene, toluene, xylene,mesitylene, cumene, cymene, styrene and divinylbenzene. Among thesecompounds, benzene is preferable.

Examples of the condensed polycyclic hydrocarbons include indene,naphthalene, azulene, fluorene, phenanthrene, anthracene,acenaphthylene, biphenylene, naphthacene, pyrene, pentalene andphenalene.

Examples of the monocyclic heterocyclic compounds include furan,thiophene, pyrrole, oxazole, isoxazole, thiazole, isothiazole, pyridine,pyrimidine, pyrroline, imidazoline and pyrazoline. Particularly,compounds containing one or more sulfur atoms are preferable. Amongthese compounds, thiophene is particularly preferable.

Examples of the condensed heterocyclic compounds include indole,isoindole, benzofuran, benzothiophene, indolizine, chromene, quinoline,isoquinoline, purine, indazole, quinazoline, cinnoline, quinoxaline andphthalazine.

Examples of the alkadienes include compounds having 4 to 6 carbon atoms,ex. butadiene, pentadiene and hexadiene.

Examples of the alkatrienes include compounds having 6 to 8 carbonatoms, ex. hexatriene, heptatriene and octatriene.

The group derived from the above examples, that is, the unit may becombined in the plural, wherein these units may be combined in a linearstate and/or in a branched state. It is preferable that these units maybe combined linearly. These units are preferably used in combinations of3 to 10 units in consideration of yield and in combinations of 3 to 8units in consideration of economical efficiency and mass-productionefficiency. Also, in these units, the same groups may be combined,groups which are all different from each other may be combined or pluraltypes of groups may be combined regularly or at random.

Also, when the unit is a group made of a five-membered ring, the bindingpositions may be any of 2,5-positions, 3,4-positions, 2,3-positions and2,4-positions. Among these positions, 2,5-positions are preferable. Inthe case of six-membered ring, the binding positions may be any of1,4-positions, 1,2-positions and 1,3-positions. Among thesecombinations, 1,4-positions are preferable. Specific examples of thisfive- or six-membered ring unit include groups derived from biphenyl(a), SC₅H₅—C₅H₅S(b), bithienyl (c), terphenyl (d), terthienyl (e),quaterphenyl (f), quaterthiophene (g), quinterphenyl (h),quinterthiophene (i), sexiterphenyl (j), sexiterthiophene (k),thienyl-oligophenylene (l), phenyl-oligothienylene (m) andphenylene-thienylene block oligomer (n). Examples of the structuralformulae of these specific examples (a) to (n) will be described below.In the above units, a and b respectively denote an integer of 2 or more,d and e respectively denote an integer of 1 or more and c and frespectively denote an integer of 0 or more (not 0 at the same time).

The unit may have a group derived from a compound, such as ethylene andbutadiene, containing one or two or more conjugate double bonds betweenneighboring five-membered ring and six-membered ring.

Specific examples of R2 include an alkyl group, oxyalkyl group,fluoroalkyl group and fluorine atom. These groups are preferablycombined linearly though they may be combined in a branched state. When,particularly, the compound of the present invention is used as afilm-forming material, a straight-chain hydrocarbon having 1 to 30 andpreferably 2 to 18 carbon atoms is preferable.

Also, the hydrophobic group R2 may be combined with any part of aπ-electron conjugate molecule and also, there is no particularlimitation to the number of the introduced hydrophobic groups insofar asthe number is 1 or more. When the number of the introduced hydrophobicgroups is plural, these hydrophobic groups may be the same or different.

The compound of the present invention contains a silanol derivativerepresented by SiX1X2X3 at its terminal. Here, X1, X2 and X3 are groupsrespectively providing a hydroxyl group when the compound is hydrolyzed.There is no particular limitation to the groups and, for example, ahalogen atom and a lower alkoxy group are given as examples. Examples ofthe halogen atom include a fluorine atom, chlorine atom, iodine atom andbromine atom. Examples of the lower alkoxy group include alkoxy groupshaving 1 to 4 carbon atoms. Examples of these alkoxy groups include amethoxy group, ethoxy group, n-propoxy group, 2-propoxy group, n-butoxygroup, sec-butoxy group and tert-butoxy group. Also, a part of the abovealkoxy group may be further substituted with other functional groups(for example, trialkylsilyl groups and other alkoxy groups).

X1, X2 and X3 may be the same or different or two of them may be thesame and the other one may be different. They are preferably the same.

Also, the compound of the present invention may have a hydrophobic groupR3 between the π-electron cojugate molecule and a silanol group. As thishydrophobic group R3, the same groups as those exemplified as R2 may beused.

The compound of the present invention is preferably those having R1: anorganic group in which 2 to 6 thienylene groups are linearly combined at2,5-positions, organic group in which 2 to 6 phenylene groups arelinearly combined at 1,4-positions or organic group in which one or morethienylene groups having bonds at 2,5-positions and one or morephenylene groups having connectors at 1,4-positions, wherein the sum ofthe both groups is 6 or less, the thienylene group and/or the phenylenegroup may have substituents selected from C1-8 alkyl groups or phenylenegroups substituted optionally with halogen atoms and a vinylene groupmay be contained between the thienylene group and/or the phenylenegroup;

R2 and R3: an alkyl group having 1 to 18 carbon atoms; and

X1 to X3: a halogen atom or an alkoxy group having 1 to 4 carbon atoms.

Compounds A to M that are preferable as the compound of the presentinvention will be described below.

The compound of the present invention may be produced by a Grignardreaction or lithium dissociation reaction between a Grignard's reagentor a lithium compound produced from a π-electron conjugate molecule anda silanol derivative. Specifically, the π-electron conjugatemolecular-containing silicone compound represented by the formula (I) or(II) may be produced by reacting a compound represented by the formula(III) or (IV):R2-R1-Z  (III)R2-R1-R3-Z  (IV)wherein R1 to R3 are as defined above and Z represents MgX (where Xrepresents a halogen atom) or lithium), with a compound represented bythe formula (V):

wherein X1, X2 and X3, which may be the same or different, respectivelyrepresent a group providing a hydroxyl group when the compound ishydrolyzed and Y represents a hydrogen atom, a halogen atom or a loweralkoxy group. In this production method, examples of the halogen atominclude a fluorine atom, chlorine atom and bromine atom and examples ofthe lower alkoxy group include a methoxy group, ethoxy group and propoxygroup.

The temperature in the Grignard reaction or lithium dissociationreaction is, for example, −100 to 150° C. and preferably −20 to 100° C.The reaction time is, for example, about 0.1 to 48 hours. The reactionis usually run in an organic solvent having no influence on thereaction. Examples of the organic solvent having no influence on thereaction include hydrocarbons such as hexane, pentane, benzene andtoluene, ether type solvents such as diethyl ether, dipropyl ether,dioxane and tetrahydrofuran (THF) and aromatic hydrocarbons such asbenzene and toluene. These organic solvents may be used either singly oras a mixture solution. Among these solvents, diethyl ether and THF arepreferable. In the reaction, a catalyst may be optionally used. As thecatalyst, a known catalyst such as a platinum catalyst, palladiumcatalyst or nickel catalyst may be used.

The method of synthesizing a silicon compound according to the presentinvention will be explained. The reaction temperature and the reactiontime in the following synthetic methods are the same as those mentionedabove and are, for example, −100 to 150° C. and 0.1 to 48 hours.

The following explanations are furnished as to a synthetic example of aprecursor of the organic group (R1) constituted of a unit derived frombenzene which is an example of the monocyclic aromatic hydrocarbon and aunit derived from thiophene which is an example of the monocyclicheterocycle compound. A precursor of heterocyclic compounds containing anitrogen atom or an oxygen atom may also be produced in the same manneras in the production of a sulfur-containing heterocyclic compound suchas thiophene.

As a method of synthesizing the precursor constituted of a unit derivedfrom benzene or thiophene, a method in which, first, the reaction partof benzene or thiophene is halogenated and then, a Grignard reaction isutilized is effective. The use of this method makes it possible tosynthesize a precursor in which the number of benzenes or thiophenes iscontrolled. Besides the method in which a Grignard's reagent is used,the precursor may be synthesized by coupling utilizing a proper metalcatalyst (Cu, Al, Zn, Zr or Sn, etc.).

As to thiophene, the following synthetic methods may be utilized, aswell as the method to which a Grignard's reagent is applied.

Specifically, first, the 2′-position or 5′-position of thiophene ishalogenated (for example, chlorinated). Examples of the halogenatingmethod include one-equivalent N-chlorosuccinimide (NCS) treatment andphosphorous oxychloride (POCl₃) treatment. As the solvent at this time,for example, a chloroform/acetic acid (AcOH) mixture solution or DMF maybe used. Also, halogenated thiophenes are reacted among them under thepresence of tris(triphenylphosphine)nickel (PPh)₃Ni as a catalyst in aDMF solvent, whereby these thiophenes can be combined at the halogenatedparts resultantly.

Moreover, divinylsulfone is added to the halogenated thiophene to couplethe both, thereby forming a 1,4-diketone body. In succession, a LawessonReagent (LR) or P₄S₁₀ is added to the 1,4-diketone body and theresulting mixture is refluxed overnight in the former case or for 3hours in the latter case to cause a ring-closing reaction. As a result,a precursor having the number of thiophenes larger by one than the totalnumber of the coupled thiophenes can be synthesized.

The number of thiophene rings can be increased by utilizing the abovereaction of thiophene.

The above precursor may be halogenated at its terminal in the samemanner as in the case of the raw material used for the synthesis.Therefore, the precursor is halogenated and then, reacted with, forexample, SiCl₄ to obtain a silicon compound (simple benzene or simplethiophene compound) which has a silyl group at its terminal and isprovided with an organic group (R1) constituted only of a unit derivedfrom benzene or thiophene.

One example of a method of synthesizing the precursor of the organicgroup constituted only of benzene or thiophene and one example of amethod of silylating the precursor are shown in the following (A) to(D). In this case, in the synthetic example of the precursor constitutedonly of thiophene, only reactions of thiophene trimers into hexamers orheptamers are shown. However, if this thiophene is reacted with athiophene having different unit number, precursors other than the abovehexamers or heptamers can be formed. For example, if 2-chlorobithiophenechlorinated by NCS after 2-chlorothiophene is coupled is reacted in thesame manner as in the following method, a thiophene tetramer or pentamercan be formed. Moreover, if the thiophene tetramer is chlorinated byNCS, a thiophene octamer or nonamer can also be formed.

There is, for example, a method using a Grignard reaction as a methodused to obtain a block type organic group precursor by directly bindingunits obtained by binding units derived from a specified number ofthiophenes or benzenes. If the precursor is reacted with SiCl₄ orHSi(OEt)₃, a target silicon compound can be obtained. Also, among theabove compounds, the compound having a terminal alkoxy group and a silylgroup can be synthesized in the condition that it is bound with the rawmaterial in advance because it has low reactivity. As synthetic examplesin this case, the following method may be applied.

First, an opposite terminal of a silyl group of a simple benzene orsimple thiophene compound is halogenated (for example, brominated) andthen, the functional group combined with the silyl group is convertedfrom the halogen into an alkoxy group by a Grignard reaction. Insuccession, n-BuLi and B(O-iPr)₃ are added to carry out debrominationand the formation a boron compound. The solvent used at this time ispreferably an ether. Also, the reaction when the boron compound isformed is preferably run in two stages: the reaction is run at −78° C.in the first stage to stabilize the reaction in the initial stage and attemperatures raised gradually from −78° C. to ambient temperature in thesecond stage. In the meantime, an intermediate of a block type compoundis produced by a Grignard reaction using benzene or thiophene havinghalogen groups (for example, a bromo group) at both terminals.

In this state, if the intermediate having unreacted bromo group and theabove boron compound are placed in, for example, a toluene solvent andare reacted completely at a reaction temperature of 85° C. in thepresence of Pd(PPh₃)₄ and Na₂CO₃, it is possible to cause coupling. As aresult, a silicon compound having a silyl group at the terminal of ablock type compound can be synthesized.

One example of the synthetic routes of silicon compounds (E) and (F) byusing such a reaction is shown below. Here, the compound having ahalogen group (for example, a bromo group) and a trichlorosilyl group atboth terminals of the unit derived from benzene or thiophene may beformed by reacting p-phenylene or 2,5-thiophenediyl with a halogenatingagent (for example, NBS) to halogenate both terminals and then byreacting the reaction product with SiCl₄ to substitute one of theterminal halogen with a trichlorosilyl group.

As a method of synthesizing a precursor in which units derived frombenzene or thiophene and vinyl groups are alternately bound, forexample, the following method may be applied. Specifically, a rawmaterial made of benzene or thiophene provided with a methyl group atits reaction position is prepared and then, its both terminals arebrominated by using 2,2′-azobisisobutyronitrile (AIBN) andN-bromosuccinimide (NBS). Thereafter, PO(OEt)₃ is reacted with the bromobody to form an intermediate. In succession, a compound having analdehyde group at its terminal is reacted with the intermediate in, forexample, a DMF solvent by using NaH, whereby the above precursor can beformed. The resulting precursor has a methyl group at its terminal.Therefore, if the methyl group is further brominated and the abovesynthetic route is applied again, a precursor more increased in thenumber of units can be formed.

If the obtained precursor is brominated using, for example, NBS, thebrominated part can be reacted with SiCl₄. Therefore, a silicon compoundhaving SiCl₃ at its terminal can be formed. One example of the syntheticroutes of precursors (G) to (I) differing in length and silicon compound(J) is shown below by the above reaction.

Any of these compounds may use a raw material having a side chain (forexample, an alkyl group) at a specified position. Specifically, if forexample, 2-octadecylterthiophene is used as a raw material,2-octadecylsexithiophene can be obtained as the precursor (A) by theabove synthetic route. Therefore,2-octadecylsexithiophenetrichlorosilane can be obtained as the silanecompound (C). Similarly, any of the above compounds (A) to (J) having aside chain can be obtained if a raw material having a side chain at aspecified position is used.

Next, a method of introducing a side chain (hydrophobic group: R2) willbe explained. In the case where, like the compound of the presentinvention, a compound has a highly reactive functional group at itsterminal, it is preferable to introduce the side chain into the rawmaterial or the intermediate as mentioned above or to introduce the sidechain after the side chain is converted into a silyl group having aalkoxy group having relatively low reactivity. As the side chain to beintroduced, an alkyl chain is preferable in the case of intendingprimarily to improve the solubility. As to the introduction method, acoupling reaction using a metal catalyst including a Grignard reactionmay be applied after the position into which an organic group is to beintroduced is halogenated. As one example, a method of synthesizingπ-electron conjugate molecule-containing silicon compound of the presentinvention in the case where the side chain is an alkyl chain will beshown below.

In the above synthetic method, only the case where the side chain is analkyl chain is shown. However, an alkoxy group may be introduced usingthe same method.

Also, the raw material used in the above synthetic example is a commonreagent, which is commercially available from a reagent maker and can beutilized. The CAS number and the purity of a reagent in the case wherethe reagent maker is Kishida Kagaku are shown below. TABLE 1 Rawmaterial CAS No. Purity 2-chlorothiophene 96-43-5 98%2,2′,5′,2″-terthiophene 1081-34-1 99% Bromobenzene 108-86-1 98%1,4-dibromobenzene 106-37-6 97% 4-bromobiphenyl 92-66-0 99%4,4′-dibromobiphenyl 93-86-4 99% p-terphenyl 92-94-4 99%α-bromo-p-xylene 104-81-4 98%

The compounds (I) and (II) obtained in this manner may be isolated fromthe reaction solution and purified by known measures such astrans-dissolution, concentration, solvent extraction, fractionation,crystallization, recrystallization and chromatography.

The compound of the present invention may be formed into a thin film inthe following manner. First, the compound of the present invention isdissolved in a nonaqueous type organic solvent such as hexane,chloroform or carbon tetrachloride. A base body (preferably a base bodyhaving active hydrogen such as a hydroxyl group or carboxyl group) onwhich a thin film is to be formed is dipped in the obtained solution andthen pulled up. Or, the obtained solution may be applied to the surfaceof the base body by utilizing a coating method such as a spin coatingmethod or ink jet method. After that, the base body is washed with anonaqueous organic solvent and then with water, and allowed to stand orheated to dry the base body to fix the thin film. This thin film may beused directly as electric materials or may be further subjected totreatment such as electrolytic polymerization. The compound of thepresent invention can be formed as a self-organized thin film (forexample, a monomolecular film) with ease.

The compound of the present invention has a network structureconstituted from a silicon atom and an oxygen atom, is reduced in thedistance between neighboring π-electron conjugate molecules and ishighly crystallized. Also, when the unit is arranged linearly, thedistance between neighboring π-electron conjugate molecules is smaller,making it possible to obtain a material capable of forming a highlycrystallized organic thin film.

If, at this time, the hydrophobic group R3 exists between then electronconjugate molecule and a silanol group, the film is packed more highlydensely by the hydrophobic interaction at this part. This issignificantly exhibited when R3 is a straight-chain hydrocarbon group.

EXAMPLES

Synthetic examples of the π-electron conjugate molecule-containingcompound of the present invention will be described. Hereinafter, astraight-chain alkyl unit is represented by the number of carbon atoms.For example, an octadecyl group is shown as C18. Also, a phenylene unitand a thiophene unit are represented by P and Th respectively and thenumerals behind the symbols show the numbers of phenylene units andthiophene units which are bound linearly. For example, a terthiophenemolecule is noted by Th3.

Synthetic Example 1 Synthesis of C18-P3 using 1-octadecane and terphenyland synthesis of C18-P3-SiCl₃ using C18-P3 and tetrachlorosilane

C18-P3 was synthesized by the following method.

First, a specified amount of 1-octadecane was reacted with an equivalentamount of butyl lithium in THF to add lithium to octadecane. Insuccession, the lithium-addition 1-octadecane was reacted with1-bromo-phenyl in THF to synthesize C18-P3.

Moreover, C18-P3 was brominated and reacted with SiCl₄ to synthesize thefollowing C18-P3-SiCl₃ (yield 45%).

The obtained compound was subjected to measurement of infraredabsorption spectrum and as a result, absorption originated from SiC wasobserved at 1062 cm⁻¹, to confirm that the compound had a SiC bond.Also, the ultraviolet-visible absorption spectrum of the solutioncontaining the compound was measured and as a result, absorption wasobserved at a wavelength of 280 nm. This absorption is caused π→π*transition of a terphenyl molecule contained in the molecule, and it wastherefore confirmed that the compound contained a terphenyl molecule.

Moreover, the compound was subjected to measurement of nuclear magneticresonance (NMR). In this case, because this compound had highreactivity, it is difficult to carry out NMR measurement directly.Therefore, the NMR was measured after the compound was reacted withethanol (at this time, the generation of hydrogen chloride wasconfirmed) to exchange the terminal chlorine for an ethoxy group. As aresult, the following peaks were obtained.

7.90 ppm to 7.25 ppm (m) (originated from a 12H aromatic)

2.60 ppm to 2.5 ppm (m) (originated from a 6H ethoxy group-ethyl group)

1.40 ppm to 1.3 ppm (m) (originated from a 9H ethoxy group-methyl group,37H methylene and methyl group)

From these results, this compound was confirmed to be C18-P3-SiCl₃.

Also, the obtained compound had a solubility about 2.8 times that ofP3-SiCl₃ (solubility: about 2.0 mg/ml) in 1 ml of THF, showing that itexhibited high solubility in an organic solvent.

Synthetic Example 2

Synthesis of C18-Th4 using 1-octadecane and quaterthiophene andsynthesis of C18-Th4-Si(OCH₃)₃ using C18-Th4 and tetramethoxysilane

Further, C18-Th4 was brominated and then reacted with tetramethoxysilaneto synthesize the following C18-Th4-Si(OCH₃)₃.

The obtained compound was subjected to measurements of infraredabsorption spectrum, ultraviolet-visible absorption spectrum and NMR asExample 1, to confirm that this compound was C18-Th4-Si(OCH₃)₃.

Also, the obtained compound had a solubility about 9.5 times that ofTh4-SiCl₃ (solubility: about 1.0 mg/ml) in 1 ml of toluene, showing thatit exhibited high solubility in an organic solvent.

Synthetic Example 3

Synthesis of C18-Th4 using 1-octadecane and quaterthiophene andsynthesis of C18-Th4-Si(OC₂H₅)₃ using C18-Th4 and tetraethoxysilane

C18-Th4 was synthesized in the same method as in Example 2. Insuccession, the thiophene part of C18-Th4 was brominated and thenreacted with tetraethoxysilane to synthesize the followingC18-Th4-Si(OC₂H₅)₃.

The obtained compound was subjected to measurements of infraredabsorption spectrum, ultraviolet-visible absorption spectrum and NMR asExample 1, to confirm that this compound was C18-Th4-Si(OC₂H₅)₃.

Also, the obtained compound had a solubility about 10 times that ofTh4-SiCl₃ (solubility: about 1.0 mg/ml) in 1 ml of toluene, showing thatit exhibited high solubility in an organic solvent.

Synthetic Examples 4 to 13

In the above Synthetic Examples 1 to 3, only the methods of synthesizingC18-P3-SiCl₃, C18-Th4-Si(OCH₃)₃ and C18-Th4-Si(OC₂H₅)₃ are shown.However, organic silicon compounds having the above structural formulaeD to M binded silicon directly with an alkyl (or an alkoxy) group and anaromatic group can be synthesized in the same method as in abovesynthetic Examples 1 to 3.

Examples of the organic solvent that can dissolve the organic silanecompound of the present invention include, besides THF and toluene usedin the above Synthetic Examples, nonaqueous organic solvents such ashexane, n-hexadecane, methanol, ethanol, IPA, chloroform,dichloromethane, carbon tetrachloride, 1,1-dichloroethane,1,2-dichloroethane, dimethyl ether, diethyl ether, DMSO, xylene andbenzene, though different depending on functional groups and silyl groupcontained in the compound.

All the compounds obtained in the above Synthetic Examples 1 to 13 havethe characteristics that each has higher solubility than compoundshaving no hydrophobic group and high generality in the formation of afilm utilizing, for example, a solution system.

The π-electron conjugate molecule-containing silicon compound contains ahydrophobic group at its side chain and therefore has the advantage thatit is improved in solubility in a hydrophobic organic solvent.Therefore, even a material increased in the number of π-electronconjugate units, which material is not conventionally used in a solutionprocess, can be applied and it is therefore possible to provide afunctional organic thin film having higher conductivity.

Particularly, when the hydrophobic group, the π-electron conjugatemolecule and the silanol derivative part are bound in series, the sterichindrance of the structural molecules is very reduced, so that a highlyoriented organic thin film having a small intermolecular distance can beprovided.

Also, the π-electron conjugate molecule in the present invention is anamphipatic molecule having both hydrophobic and hydrophilic molecules.Emulsion particles can be obtained by dispersing the n-electronconjugate molecule in, for example, an organic solvent. Since theparticle contains the π-electron conjugate molecule and therefore hasconductivity. This particle can be combined with a silanol group byallowing the solvent to contain water in advance and it is possible toencapsulate emulsion particles according to the need. The π-electronconjugate molecule of the present invention may be applied to thecapsulation technologies.

Example 3

An example in which the compound of the present invention is used toform a functional organic thin film is described.

Using C18-Th4-Si(OC₂H₅)₃ obtained in Synthetic Example 3, a functionalthin film was formed in the following manner.

First, a quartz substrate was dipped in a mixed solution of hydrogenperoxide and concentrated sulfuric acid (mixing ratio: 3:7) for one hourto carry out hydrophilic treatment of the surface of the quartzsubstrate. After that, C18-Th4-Si(OC₂H₅)₃ was dissolved in a nonaqueousorganic solvent (for example THF) to obtain a 10 mM C18-Th4-Si(OC₂H₅)₃solution. The obtained substrate was dipped in this solution in an inertatmosphere for 30 minutes. Then, the substrate was pulled up slowly andthen washed with a solvent to form a film on the quarts substrate.

The quartz substrate on which a film was formed was subjected tomeasurement of ultraviolet-visible absorption spectrum and tomeasurement of a film thickness using ellipsometry. It was confirmedfrom these results that a monomolecular film containingC18-Th4-Si(OC₂H₅)₃ was formed on the quartz substrate.

Also, when the formed monomolecular film was subjected to a SPM deviceto observe its surface, a periodic structure was observed. When thismonomolecular film having a periodic structure was subjected to ascratch strength test using the cantilever of the SPM device, it wasconfirmed that the stress of the cantilever necessary to disturb theperiodic structure of the monomolecular film (C18-Th4-Si(OC₂H₅)₃ thinfilm) was 1.2 times that of Th4-Si(OC₂H₅)₃. This reason is considered tobe that the addition of a straight-chain hydrocarbon group as the sidechain increases the molecular interaction with neighboring moleculeswhen the monomolecular film is formed. Therefore, the use of thecompound of the present invention made it possible to form an organicthin film which had strong durability and was closely packed by thestrong interaction between molecules.

1. A π-electron conjugate molecule-containing silicon compoundrepresented by the formula (I):

wherein R1 represents an organic group obtained by combining two or moreunits constituting plural π-electron conjugate systems, R2 represents ahydrophobic group and X1 to X3, which may be the same or different,respectively represent a group providing a hydroxyl group when it ishydrolyzed or a hydrogen atom.
 2. A π-electron conjugatemolecule-containing silicon compound represented by the formula (II):

wherein R1, R2 and X1 to X3 are as defined above and, R3 represents ahydrophobic group.
 3. A π-electron conjugate molecule-containing siliconcompound according to claim 1, wherein R2 in said formula (I) or each ofR2 and R3 in the formula (II) is a straight-chain hydrocarbon grouphaving 1 to 30 carbon atoms.
 4. A π-electron conjugatemolecule-containing silicon compound according to claim 3, wherein saidR3 is a straight-chain alkyl group having 1 to 30 carbon atoms.
 5. Aπ-electron conjugate molecule-containing silicon compound according toclaim 1, wherein said R1 is an organic group in which units constituting3 to 10 π-electron conjugate systems are linearly combined.
 6. Aπ-electron conjugate molecule-containing silicon compound according toclaim 1, wherein said units constituting plural π-electron conjugatesystems is selected from the group consisting of groups derived from amonocyclic aromatic hydrocarbon compound, a condensed polycyclichydrocarbon, a monocyclic heterocyclic compound, a condensedheterocyclic compound, an alkene, an alkadiene, and an alkatriene andsaid R1 is an organic group in which one or more units selected fromsaid group are combined linearly.
 7. A π-electron conjugatemolecule-containing silicon compound according to claim 6, wherein saidunit constituting a π-electron conjugate system is a group derived frombenzene or thiophene.
 8. A method of producing a π-electron conjugatemolecule-containing silicon compound comprising reacting a compoundrepresented by the formula (III) or (IV):R2-R1-R3-Z  (III)R2-R1-R3-Z  (IV) wherein R1 to R3 are as defined above and Z representsMgX, wherein X represents a halogen atom or Li, with a compoundrepresented by the formula (V):

wherein X1 to X3 are as defined above and Y represents a hydrogen atom,a halogen atom or a lower alkoxy group to produce the π-electronconjugate molecule-containing silicon compound represented by theformula (I) or (II):

wherein R1 to R3 and X1 to X3 are as defined above.
 9. A method ofproducing a π-electron conjugate molecule-containing silicon compoundaccording to claim 8, wherein the group R is derived from a compoundobtained by repeating a process one or more times in which a specifiedbinding position of a raw material selected from a monocyclic aromatichydrocarbon and a monocyclic heterocyclic compound is halogenated andthen, the raw material is made to enter into a Grignard reaction to binda specified number of the raw materials.
 10. A method of producing aπ-electron conjugate molecule-containing silicon compound according toclaim 8, wherein the unit constituting the group R is derived fromthiophene and the group R is derived from a compound obtained byrepeating a process one or more times in which a specified bindingposition of thiophene is halogenated and then, obtained thiophenehalides are reacted among them in the presence of NCS or POCl₃ to bind aspecified number of thiophenes.
 11. A method of producing a π-electronconjugate molecule-containing silicon compound according to claim 8,wherein the unit constituting the group R is derived from thiophene andthe group R is derived from a compound obtained by repeating a processone or more times in which a specified binding position of thiophene ishalogenated, then, obtained thiophene halide is reacted withdivinylsulfone to obtain a 1,4-diketone body in which thiophene is boundwith each side of the succinyl group and the 1,4-diketone body is madeto enter into a ring-closure reaction in the presence of a Lawessonagent or P₄S₁₀ to bind a specified number of thiophenes.
 12. A method ofproducing a π-electron conjugate molecule-containing silicon compoundaccording to claim 8, wherein the group R is derived from a compoundobtained by repeating a process one or more times in which a methylgroup of a raw material selected from a monocyclic aromatic hydrocarbonand a monocyclic heterocyclic compound having the methyl group at aspecified binding position is halogenated, then this halogen issubstituted with a pentavalent phosphorous compound and the obtainedcompound is reacted with a raw material selected from a monocyclicaromatic hydrocarbon and a monocyclic heterocyclic compound having analdehyde group at each specified position to bind a specified number ofthe raw materials.
 13. Aπ-electron conjugate molecule-containing siliconcompound according to claim 2, wherein R2 in said formula (I) or each ofR2 and R3 in the formula (II) is a straight-chain hydrocarbon grouphaving 1 to 30 carbon atoms.
 14. A π-electron conjugatemolecule-containing silicon compound according to claim 2, wherein saidR1 is an organic group in which units constituting 3 to 10 π-electronconjugate systems are linearly combined.
 15. A π-electron conjugatemolecule-containing silicon compound according to claim 2, wherein saidunits constituting plural π-electron conjugate systems is selected fromthe group consisting of groups derived from a monocyclic aromatichydrocarbon compound, a condensed polycyclic hydrocarbon, a monocyclicheterocyclic compound, a condensed heterocyclic compound, an alkene, analkadiene, and an alkatriene and said R1 is an organic group in whichone or more units selected from said group are combined linearly.